1. Field of the Invention
The present invention relates generally to inserting or running wellbore tubulars into a wellbore and, more particularly, to a collar load support system for picking up and lowering a wide size range of wellbore tubulars into the wellbore.
2. Description of the Background
Corrosion resistant alloy is useful in wellbore tubulars including casing, production tubing, and the like, to avoid premature failure of the wellbore tubulars in hostile environments. Severe corrosive action may occur in hostile environments such as deep, high pressure gas wells. Although such wells may be highly productive, they also tend to be expensive to drill and to workover. Therefore, these wells are suitable for extra precautions taken to extend the productive life thereof such as corrosion resistant alloy wellbore tubulars. Traditional procedures and hardware used to carry out installation of tubing may produce marks on corrosion resistant alloy wellbore tubulars because traditional procedures rely on toothed inserts or dies and gripping mechanisms that force the die or insert teeth radially inwardly against the pipe outer diameter. Ideally, complete elimination of the injurious die marks and associated necessary cold working for such tubulars would permit optimum performance of the corrosion resistant alloy, minimum cost of a string of corrosion resistant alloy, and the least weight thereof.
One wellbore tubular running system, which is disclosed in U.S. Pat. No. 5,083,356, issued Jan. 28, 1992, to Gonzalez et al., and which is incorporated herein by reference, teaches a method for non-abrasively running tubing. The method includes the steps of suspending the tubing from the face of the uppermost collar of the tubing by resting the face upon a support shoulder, making up a new tubular with a collar into a tubular unit, attaching a non-abrasive lift unit to a tubular unit, stabbing the new tubular into the upper collar, non-abrasively making the connection tight, and lifting the unit to raise the string.
The above wellbore tubular running system makes use of a shock table and landing spear that has several purposes. The landing spear engages the lifting unit, or load transfer sleeve, and is supported by the shock table. One of the purposes of the shock table is to reduce the dynamic effects of decelerating the tubing string. This deceleration occurs when the wellbore tubular string weight is transferred from the elevator to the shock table through a landing spear. If desired, the table compression rate may be provided in two stages although one stage could also be used. For example only of a two-stage system, from 0 to 60 tons, the load could be absorbed at a rate of 17.5 tons/inch and once the loading exceeds 60 tons, the compression rate could increase to 55 tons/in of deflection. Mechanical stops could be finally engaged at 160 tons. Essentially, the table compression rate increases the time span over which the load is applied regardless of the specific spring rates, the final mechanical stop and whether or not more than one stage of table compression rate is provided. The increased time interval significantly decreases the dynamic forces applied to the tubular coupling face as taught by the method.
One of the problems of the above wellbore tubular system is that, for practical purposes, the system is limited in the size of the wellbore tubulars, including variable size items in the tubular string, which can be readily inserted into the wellbore. It would be desirable to provide means that can be used that would allow couplings and other large items to pass through the shock table and landing spear with ease while still maintaining full functioning of the shock table and landing spear. Another problem of the wellbore tubular running system relates to the shock table and the amount of space it takes up thereby requiring personnel to work on elevated work platforms, scaffolding, and the like in the midst of rather heavy equipment. Working on elevated work platforms tends to be more confining, more prone to slow downs, with less room for personnel to avoid accidents.
Consequently, the above referenced prior art does not disclose means for eliminating the problems associated with existing non-abrasive wellbore tubular running systems. It would be desirable to provide a system suitable for running corrosion resistant alloy wellbore tubulars that permits more space on the rig floor. It would be highly desirable to allow the personnel to work on the rig floor rather than on scaffolding. As well, it would be desirable to provide such a system that is more flexible with respect to variations in wellbore tubular sizes, including casing, and permits couplings and large items to pass through the shock table and landing spear easily. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems.
The present invention was designed to provide more efficient operation to thereby improve flexibility of operation and to reduce drilling costs due to decreased time required for using different size wellbore tubulars, collars, and pipe string components.
Therefore, it is an object of the present invention to provide an improved handling system for holding and lowering wellbore tubulars, especially a wide range of tubulars including pipes, production tubing, as well as large tubulars such as casing.
Another object of the present invention is to provide a handling system that is easier to operate and is safer for rig personnel.
A feature of the present invention is a split sectioned landing spear for which may be split open to allow a large item to easily pass.
These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. However, the invention is not limited to these objects, features, and advantages.
Therefore, the present invention provides for a handling system for holding and lowering wellbore tubulars for use with a rig having a traveling block and a rig floor. The rig floor defines an opening therethrough for the wellbore tubulars. A plurality of collars is provided for interconnecting the wellbore tubulars. The system comprises a sleeve for engaging the plurality of collars and a landing spear for engaging the sleeve. A shock table is provided with a shock table body. A portion of the shock table body extends through the rig floor within the opening. The shock table comprises a compressible section with a compressible surface supported by the compressible section. The compressible surface supports the landing spear.
In a preferred embodiment, a radially outwardly extending member is secured to one end of the shock table body for engagement with the rig floor and for supporting the shock table within the opening. The radially outwardly extending member may preferably be a flange.
The landing spear is preferably pivotally mounted with respect to the compressible surface. The landing spear may comprise separable elements, wherein each of the separable elements may be pivotally mountable with respect to the compression surface. The landing spear has a base for engagement with the compression surface and may have a conical profile in one embodiment. The landing spear has an outer circumference and may be split into at least two sections with each of the two sections forming a portion of the outer circumference. A connection may be provided between the at least two sections and the compression table. The connection may be a pivotal connection to permit pivotal movement between the at least two sections and the compression table.
In one method of the present invention, steps are provided such as mounting a shock table within the opening in the rig floor such that a substantial portion of the shock table is below a surface of the rig floor. Other steps may include providing a landing spear for receiving a weight of the wellbore tubulars and providing a compressible surface for the shock table such that the compressible surface is moveable with respect to the rig floor in response to tension applied thereto through the landing spear. In one embodiment, a step is provided for pivotally interconnecting the landing spear with respect to the shock table.
In other words, one embodiment of the invention may include a shock table mountable with respect to the rig floor and a landing spear for supporting a weight of the wellbore tubulars transferred to the landing spear through the load transfer sleeve from respective of the plurality of collars. The landing spear may have at least two sections with each of the sections secured to the shock table by one or more connections that allow each of the sections to be moveable with respect to the shock table between a closed position and an open position. One or more of the connections may further comprise one or more hinges.
In operation, one embodiment of a method for a handling system for wellbore tubulars may provide steps such as the step of suspending a wellbore tubular string by supporting a weight of the wellbore tubular string on a load transfer sleeve that engages a downward face of an upper collar of the wellbore tubular string wherein the weight of the wellbore tubular string may be received by a landing spear. The landing spear preferably has two or more landing spear sections. Additional operational steps may include lifting an additional wellbore tubular via a load transfer sleeve for attachment to the wellbore tubular string, stabbing a pin end of the additional wellbore tubular into the upper collar, making the pin end and the upper collar connection tight, lifting the wellbore tubular string, and opening the landing spear by moving the landing spear sections radially outwardly with respect to the wellbore tubular string.
The method of operation may include compressing a compressible support surface in response to the weight of the wellbore tubular string at a selected rate of compression and pivotally attaching the landing spear with respect to the compressible support surface. In a preferred embodiment, the method further comprises mounting a shock table body for supporting the compressible support surface such that at least a portion of the shock table body is mounted beneath a rig floor.